Re: [RFC] omap3-isp G_FMT & ENUM_FMT

[Michael Jones <michael.jones@matrix-vision.de>]

Hi Laurent,

On 07/27/2012 01:32 AM, Laurent Pinchart wrote:
> Hi Michael,
>
> On Thursday 26 July 2012 16:22:17 Michael Jones wrote:
>> On 07/26/2012 04:05 PM, Laurent Pinchart wrote:
>>> On Thursday 26 July 2012 13:59:54 Michael Jones wrote:
>>>> Hello,
>>>>
>>>> I would like to (re)submit a couple of patches to support V4L2 behavior
>>>> at the V4L2 device nodes of the omap3-isp driver, but I'm guessing they
>>>> require some discussion first.
>>>
>>> Indeed.
>>>
>>> The main reason why the OMAP3 ISP driver implements G_FMT/S_FMT as it does
>>> today is to hack around a restriction in the V4L2 API. We needed a way to
>>> preallocate and possibly prequeue buffers for snapshot, which wasn't
>>> possible in a standard-compliant way back then.
>>>
>>> The situation has since changed, and we now have the VIDIOC_CREATE_BUFS
>>> and VIDIOC_PREPARE_BUF ioctls. My plan is to
>>>
>>> - port the OMAP3 ISP driver to videobuf2
>>> - implement support for CREATE_BUFS and PREPARE_BUF
>>> - fix the G_FMT/S_FMT/ENUM_FMT behaviour
>>
>> What will the G_FMT/S_FMT/ENUM_FMT behavior be then?  Can you contrast
>> it with the behavior of my patches?  If the behavior will be the same
>> for user space, and your proposed changes won't be in very soon, can we
>> use my patches until you make your changes?
>
> At the moment the driver accepts any format you give it in a S_FMT call,
> regardless of the format of the connected pad. The reason for that is to allow
> VIDIOC_REQBUFS to allocate buffers for an arbitrary size.
>
> With CREATE_BUFS and PREPARE_BUFS support, G_FMT, S_FMT and ENUM_FMT should
> return the format of the connected pad.
>

OK, so this sounds like the same behavior I'd like to add before 
CREATE_BUFS and PREPARE_BUFS support is in.  My other question was if 
this is the case, can we use my approach until your planned changes are in?

-Michael

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